Heat exchangers may be employed in various applications to exchange heat between two fluids. For example, a first fluid at a higher temperature may be passed through a first passageway, while a second fluid at a lower temperature may be passed through a second passageway. The first and second passageways may be in contact or close proximity, allowing heat from the first fluid to be passed to the second fluid. Thus, the temperature of the first fluid may be decreased and the temperature of the second fluid may be increased.
Heat exchangers may be employed in conjunction with gas turbine engines. For example, to improve operating efficiency, heat from one portion of a gas turbine may be transferred to another portion of the gas turbine. As another example, heat from one portion of a gas turbine may be transferred outside of the gas turbine, allowing cooling of a portion of gas turbine (or cooling of a flow within the turbine).
Gas turbines may be utilized in challenging design environments. For example, gas turbines may be employed for propulsion in aircraft. Such an environment may provide a number of challenges to the design of and/or materials used for heat exchangers. For example, high temperatures (e.g., about 300 degrees Celsius or higher) may be encountered in such environments. Also, low weight constraints may be present in such environments. Further still, the amount of drag permitted through one or more passages of a heat exchanger may be limited in such environments.
Conventionally, heat exchangers use metals (e.g., copper, aluminum, or the like) for improved heat transfer due to the relatively high thermal conductivity of metals. However, various metals may be inappropriate for certain applications due to cost, presence of high temperatures, weight requirements, or the like. For example, Aluminum is a generally good thermal conductor and relatively lightweight, but may be inappropriate for operating environments having high temperatures, for example about 300 degrees Celsius or above, as Aluminum loses strength at higher temperatures and may have inadequate strength for applications having operating temperatures of about 300 degrees Celsius or above. Other metals, or other materials with relatively high thermal conductivity may be expensive to obtain and/or form. Further, other metals or materials may weigh more than desired for applications where weight is at a premium.